Understanding rigid body physics
I'm no expert, but I'll see if I can help quickly.  Is the outer mesh with normals pointed in the right idea?  You might need to give it some thickness somehow, perhaps by using a solidify modifier on its surfaces.  Or maybe the whole thing is trying to behave as a solid (even though you say the normals face inwards) ...if the tutorial got you here, then that sounds wrong.  But just because it is being displayed as a wireframe doesn't mean it isn't a solid.  (I don't think; I've been away from blender for a minute)